The present invention generally relates to methods and systems for performing pre-registration/pre-authentication and reserving resources in wireless communications networks and more specifically to the use of such methods and systems in an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and an evolved High Rate Packet Data (eHRPD) network.
Fourth-generation (4G) wireless systems are end-to-end (from radio access networks to core networks) all-IP systems. 4G systems are expected to upgrade existing communication networks, e.g., 3G networks, and provide secure ubiquitous IP-based communications on an “Anytime, Anywhere” basis at significantly higher data rates. 4G networks are anticipated to enhance existing services (e.g., voice, e-mail) and provide new services such as, for example, wireless broadband access, video chat, mobile TV, HDTV content and digital video broadcasting (DVB). Such networks are expected to enhance spectral efficiency (more bits/unit of time per unit of frequency) and provide more capacity, smooth handoffs, seamless connectivity, and global roaming across multiple networks.
A leading 4G wireless system is the Evolved Packet System (EPS) defined by the Third Generation Partnership Project (3GPP). It includes Long Term Evolution (LTE) for radio access networks (RANs) and Service Architecture Evolution (SAE) for the core network. It also includes an architecture for interworking with other wireless technologies such as 3GPP2 such as 3GPP2 Evolution-Data Optimized (EV-DO) to support heterogeneous wireless access technologies and to allow graceful network evolution. The radio access network and core network defined by 3GPP LTE and SAE are referred to as Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and Evolved Packet Core (EPC), respectively.
EV-DO generally refers to the 3GPP2 High Rate Packet Data (HRPD) and Evolved HRPD (eHRPD) standards. HRPD is a CDMA2000 based technology for packet transmission as described in the 3GPP2 C.S0024-A v3.0 specification. An eHRPD network provides a radio access network that supports an evolved mode of operation and provides an IP environment supporting attachment to multiple packet data networks via the 3GPP EPC. The interworking architecture is referred to as E-UTRAN and eHRPD Interworking as described in the 3GPP2 X.S0057 specification.
While standards bodies such as the 3GPP and 3GPP2 have done a significant amount of work in providing high level specifications associated with internetworking architectures (e.g., see FIG. 1), call flows (e.g., see FIG. 2) and the user equipment or mobile station/device handoffs between networks, much detail is left to implementation. For example, with reference to FIG. 2, procedures associated with when to pre-register are unspecified (see block 208 in FIG. 2). In addition, procedures for determining how long resources should be reserved are similarly open to design implementation (see block 218 in FIG. 2).
As a general matter, standard bodies usually do not standardize algorithms for performing pre-registration and pre-authentication. Accordingly, different approaches have been proposed to reduce handoff delay using pre-authentication and pre-registration. In one approach, the user equipment or mobile station, either working independently or in collaboration with one or more base stations, selects neighboring base stations it is likely to visit and participate in performing pre-registration/pre-authentication, proactive key distribution, and other procedures with candidate base stations before the user equipment or mobile station is handed off to neighboring networks. Most existing pre-registration/authentication mechanisms typically focus, however, on predicting the user equipment movement and, based on such movement, how to select target base stations that the user equipment station may be handed off to.
More specifically, some mechanisms use a centralized database associated with a server to collect the user equipment movement histories between cells to predict future handoff behavior through, for example, constructing neighbor graphs among access points in a WiFi network. However, the extra signaling messages exchanged between access points may cause consistency problem in signaling to other access points which do not employ the same algorithm. Furthermore, the centralized server is likely to become a performance bottleneck. In addition, this technique is not suitable for heterogeneous networks (networks using different access technologies) because the access points need to be under the same administrative domain.
In other mechanisms, each access point records the average required time intervals that a mobile station or the user equipment can reach its neighbors. When the user equipment requests pre-authentication, the serving access point helps to identify all the neighbors which satisfy the requirement. These mechanisms become hard to implement where there are a large number of mobile stations.
In view of existing techniques, some technical issues need to be resolved to allow for pre-registration/pre-registration to effectively reduce handoff delay. As mentioned above, one issue is when to perform pre-registration/pre-authentication. A mobile device or the or the user equipment may move at any speed and leave its current cell at any time. If pre-registration/pre-authentication is to be performed, it should be executed before actual handoff occurs. However, when the current cell is small and the user equipment is moving at high speed, the user equipment may not have sufficient time to perform pre-registration/pre-authentication with some or even any of the neighboring cells. It is therefore important to decide when and whether to trigger pre-registration/pre-authentication with neighboring cells.
Another issue is which neighboring networks or cells should pre-registration/pre-authentication be performed with. The user equipment may move in any direction and may change its moving direction at any time. It is therefore important to decide the neighboring cells with which the user equipment should perform pre-registration and pre-authentication. If pre-registration and pre-authentication is to be performed with multiple neighboring networks or cells, it is also important to determine the order in which the user equipment performs pre-registration and pre-authentication with these neighboring cells. This is because pre-registration and pre-authentication are time consuming and the mobile may leave its current cell before it completes the pre-registration and pre-authentication operations with all the neighboring networks or cells it sought to pre-register and pre-authenticate with.
Another issue is when to release network resources reserved by pre-registration/pre-authentication in the neighboring network. As illustrated in FIG. 2, once pre-registration/pre-authentication is accomplished with a neighboring cell or network, some contexts, including IP address, security keys, and mobility context, will be reserved for a particular user equipment or mobile station in the neighboring network. However, the user equipment may not visit visit some of the candidate cells with which the user equipment has performed pre-registration/pre-authentication. Therefore, it is important to delete the contexts in those cells in a timely manner.
Of utility then are systems and methods directed to addressing the issues and shortcomings associated with determining when to perform handoff and how long to reserve resources in wireless networks, and in particular all-IP wireless networks.